The present invention relates to inflatable airbag apparatuses for protection of an occupant in a motor vehicle, and more specifically, to an airbag system for deployment in front of the knee area of an occupant.
Inflatable airbags are well accepted in their use in motor vehicles and have been attributed with preventing numerous deaths in accidents. According to one report, frontal airbags reduce fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belts and airbags, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use provides clear safety benefits, and vehicle owners are frequently willing to pay the added expense for airbags.
A modem airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartment. If the vehicle has only a driver""s side airbag, the ECU may be mounted in the steering wheel. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of the inflator or gas generator which may use a combination of compressed gas and solid fuel. The inflator inflates a textile airbag to impact a passenger and prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover conceals a compartment containing the airbag module and may be located on a steering wheel, dashboard, vehicle door, or vehicle wall. The airbag cover is typically made of a rigid plastic and may be forced opened by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover is not retained, a passenger may be injured by the rigid cover as it is tossed about in the passenger compartment during an accident.
Airbag apparatuses have been primarily designed for deployment in front of the torso of an occupant. More specifically, airbags are disposed for deployment between the upper torso of an occupant and the windshield and instrument panel. During a front end collision, there is a tendency for an occupant, particularly one who is not properly restrained by a seat belt, to slide forward along the seat and xe2x80x9csubmarinexe2x80x9d under the airbag (hereinafter referenced as the xe2x80x9cprimary airbagxe2x80x9d).
In order to prevent such an occurrence, a knee airbag system has been developed to engage an occupant""s knees or lower legs and prevent submarining under the primary airbag. The knee airbag system includes a knee airbag which deploys during an accident to restrain forward movement of an occupant""s knees and legs. The knee airbag system may also include a fixed panel, referred to as a knee bolster panel, which is disposed in front of a knee airbag. The knee bolster panel provides a more rigid surface area than an airbag alone to better engage the knees or lower legs of an occupant to thereby restrain the occupant""s lower body. Nevertheless, the knee bolster panel does provide for some degree of deformation to minimize the impact to an occupant.
When the airbag is inflated, the knee bolster panel is propelled rearward, away from the instrument panel and toward the occupant. To prevent injury to the occupant and allow for proper positioning of the knee bolster panel, the knee bolster panel should be restrained. Some knee bolster systems have secured the bolster panel directly to the airbag, the airbag serving to tether the knee bolster to the instrument panel of the vehicle. However, the stress placed on the airbag in this system can cause the airbag to tear reducing the efficacy of the airbag system. Moreover, the torn airbag may release the knee bolster into the passenger compartment, potentially injuring an occupant. Moreover, it is difficult to configure the knee bolster to the airbag so that the knee bolster is positioned correctly in the event of an accident.
Some airbag systems provide tethers to better secure the knee bolster panel. One such airbag system has tethers which are positioned inside the airbag. The internal tethers may cause problems with the proper deployment of the airbag. Thus, the airbag system must be carefully designed and assembled to prevent any interference by the tethers. Because the tethers are internal to the airbag, the bolster panel must still be directly attached to the airbag which may cause the airbag to tear or malfunction.
To overcome some of the problems associated with the internally tethered knee bolster systems, externally tethered knee bolster systems have been developed. These systems provide an attachment member for securing the tethers to the instrument panel or casing of the airbag system. The tethers are sewn directly to the attachment member and to the knee bolster panel. The attachment member is then secured to the instrument panel or the casing of the airbag system.
The externally tethered systems also have a number of disadvantages. First sewing the tethers directly to the bolster panel and the attachment member can be difficult and increases the cost of the airbag system. Moreover, the tethers are generally made from long fabric strips which must be folded to properly fit within the casing of the airbag system. Overtime, the tethers may begin to unfold which may cause the airbag system to malfunction in a crash situation. Additionally, the unfolded tethers may protrude from the casing and become visible to an occupant of the vehicle. The protruding tethers may be inadvertently damaged as a vehicle occupant repeatedly brushes against them. Moreover, an occupant, especially a child, may tamper with the tethers damaging the system or potentially triggering the airbag injuring the occupant.
As a general rule, the final cost of a device is increased by the number of parts and steps required to manufacture the device. The cost of the available externally tethered airbag systems is increased by the requirement of an attachment member to secure the tethers to the instrument panel or casing of the airbag system. The cost is further increased by the complexity of sewing the tethers directly to the attachment member.
In light of the foregoing, it would be a significant advancement in the art to provide a knee airbag system with an externally tethered knee bolster. It would be an additional advancement if the airbag system had a limited number of fasteners and components. It would be a further advancement to prevent the protrusion of the tethers. It would be a further advancement if the airbag system were simple to install into a vehicle.
The present invention is an airbag system for restraining and protecting an occupant of a vehicle in the event of a crash situation. The airbag system is designed to support the knee portion of an occupant to prevent the submarining of an occupant under the primary airbag. The knee airbag system may be disposed in the lower portion of an instrument panel.
The knee airbag system may include an inflatable airbag and an inflator for inflating the airbag when the ECU detects an accident situation. The inflatable airbag and the inflator may be stored in a modular housing. The modular housing is configured to be attached to the instrument panel or fire wall of a vehicle near the knees of an occupant.
A load distributor or bolster panel may be positioned between the airbag and the occupant. The load distributor may move from a stored position adjacent the instrument panel and a deployed position away from the instrument panel. The load distributor is moved from the stored position to the deployed position as the airbag is inflated. In the deployed position, the load distributor provides support to the lower portion of an occupant""s body, thereby preventing submarining of the occupant and reducing injury.
The load distributor may be tethered to the instrument panel or the modular housing by one or more tethers external to the airbag. The tethers prevent the load distributor from flying into the passenger compartment in an accident situation. The tethers have a length sufficient to allow for the proper positioning of the deployed load distributor adjacent the lower portion of an occupant""s body.
The tethers may be secured in the stored position by one or more breakaway stitches. The breakaway stitches allow the tethers to be positioned within the modular housing in the stored position. When the inflator is activated in an accident situation, the airbag inflates and applies pressure to the breakaway stitches which give way, allowing the load distributor to move to the deployed position. The breakaway stitches provide an economical means for securing the tethers within the modular housing and preventing protrusion of the tethers or inadvertent damage or tampering with the airbag system.
The modular housing may have a stud for attachment of the inflator to the modular housing. The tethers may be attached to the modular housing in a variety of ways. For example, the tether may be secured over the stud on the side of the modular housing adjacent the airbag. The modular housing may have one or more apertures which allow access to the rear surface of the modular housing, and the tethers may be secured to the stud adjacent the external surface of the modular housing. Additionally, the apertures may be configured to clamp on the tether as the airbag is deployed.
The tethers may be attached to the load distributor in variety of ways. For example, the distributor may have one or more slots. The tether may be inserted through the slots and the ends of the tether secured to the modular housing. Alternatively, an end of the tethers may be inserted through the slots and held in place by a pin inserted through a loop at the end of the tether. The slots may have a configuration that clamps down on the tether when the airbag is inflated.
It may be desirable to attach a portion of the tether to the airbag. This attachment may be helpful in the assembly of the airbag system and aid in the positioning of the bolster panel/load distributor and tethers in the stored and deployed positions. A pivoting tether external to the airbag may be provided for proper positioning of the load distributor in the deployed position.